Sojourner Spirit

Flash, first strike, vigilance
Whenever Sojourner Spirit enters or leaves the
battlefield, choose one —
•Choose a nonbasic permanent. It phases out
and can't phase back in. (Treat it and anything
attached to it as though they don't exist.)
•If an opponent controls more lands than you,
you may search your library for a Plains card,
put it onto the battlefield, then shuffle
your library.